This invention relates to the monitoring of a vapor compression refrigerant system and more specifically to one or more embodiments of a monitor of the type which is adapted to detect and provide an indication of the onset of a system malfunction preferably in time to initiate corrective action before actual system breakdown occurs.
Refrigerant systems of the type which can advantageously employ the present invention are those used in air conditioners, heat pumps, commercial food refrigeration systems and the like, which employ a sealed refrigerant circuit comprised of a refrigerant compressor, a condenser, an evaporator and a fluid expansion device, such as an expansion valve or a capillary tube, connected between the condenser and the evaporator. Such systems may also include a filter-drier to remove particulate contaminants and to control the moisture content of the circulating refrigerant. Such systems may also include a receiver for controlling and metering the flow of liquid refrigerant from the condenser and an accumulator located upstream of the suction line leading to the compressor, the purpose of the receiver being to store excess liquid refrigerant in the system and to avoid influx of the liquid refrigerant to the compressor during start-up.
Systems of the type just described generally are operated with no provision for determining incipient malfunctions in the system, although a moisture indicator has been used in some installations. Typically, the refrigerant system is operated until system breakdown occurs at which time repair service is initiated to put the system back into operation. The down time that results from this kind of reactive maintenance program is, at best, an inconvenience for the system user and can often be very costly in terms of such things as food spoilage as in the case of commercial food refrigeration systems. It is, therefore, desirable to provide apparatus that will monitor the operation of the refrigerant system on an ongoing basis to provide an indication of the onset of a system malfunction and, where possible, to define the nature of the incipient malfunction, e.g. air leak, motor insulation deterioration, compressor malfunction, etc.
Prior publications by applicant and others have discussed the desirability of analyzing the existence and nature of contaminant gases in a refrigerant system of the type described. In one such article by applicant and Mr. R. S. Olsen entitled "Gas Analysis--a New Tool for Determining the Chemical Stability of Hermetic Systems" which was published in 1959 in Refrigeration Engineering Vol. 67, No. 2, pg. 25 et seg., the use of gas analysis was discussed as a tool for determining chemical stability of hermetic refrigerant systems and a variety of laboratory techniques were described for separating gas samples and performing the gas analysis on actual refrigerant system equipment. These sensitive and complex techniques, while suitable for laboratory purposes, are not well adapted for use on an ongoing basis under field operating conditions. Moreover, while the paper describes gas analysis as a technique for selecting suitable materials for use in designing refrigerant systems, it does not treat the use of gas analysis as a monitoring technique for field use to detect incipient systems malfunctions. In a later article entitled "Material Stabilities in Vapor Compression Refrigeration Systems" by applicant and co-authors and presented at the XIth International Congress of Refrigeration in Munich, West Germany, in 1963, there was provided a summary of gaseous contaminants formed by degradation of materials used in the construction of refrigeration systems. It was shown that materials produce characteristic gaseous products and that the rate of gas formation is an indication of the rate of degradation. As in the earlier paper, the objective of this work was to aid in selecting suitable materials for use in designing refrigerant systems. To applicant's knowledge, there is not presently available a suitable refrigerant system monitor employing techniques of contaminant gas collection and analysis as a means of detecting incipient system malfunction.
It is, therefore, an object of the invention to provide a monitor for a vapor compression refrigerant system adapted for in-situ indication of an incipient malfunction in the system.
It is a further object of the invention to provide apparatus of the type described which operates on the basis of analysis of contaminant gases in the refrigerant stream to monitor system condition.
It is a still further object of the invention to provide apparatus of the type described which is simple to construct and does not require highly skilled technicians in the field to operate or interpret.
It is yet a further object of the invention to provide monitor apparatus of the type described which provides an indication of both the existence and the nature of an incipient malfunction in the system.